The existence of substances that facilitate or even induce a psycho-physical dissociation in those who take them is not a mystery. We can find substances that are popular depending on the historical period and the cultures associated with them, but not only that.
Tradition also informs us of substances and compounds that help individuals prepare for certain experiences.
But then, when can we speak of visions? And when of hallucinations? What is the fundamental difference between the two?